Regulation of Gene Expression

Question 1

Which type of chromatin is transcriptionally active and inactive?

Answer 1

Heterochromatin = inactive
Euchromatin = active

Question 2

What is gene expression?

Answer 2

Production of functional and active gene products

Question 3

What is constitutive gene expression?

Answer 3

Made by all cells at all times
Often called housekeeping genes
Expression constant

Question 4

What is regulated gene expression?

Answer 4

Time, place, amount, in response to signals

Under very tight control

Question 5

What kind of processing does a primary transcript undergo?

Answer 5

Addition of
- 5' cap
- Poly(A) tail
Excision of introns
Splicing of exons via spliceosome

Question 6

What does the 5’ cap do?

Answer 6

Directs mRNA to ribosome

Question 7

What does the poly(A) tail do?

Answer 7

Stabilises transcript

Question 8

Are some non-coding RNAs involved in primary transcript splicing?

Answer 8

Yes

Question 9

Are mutations or variants spliced the same as the normal RNA?

Answer 9

No, they produce alternative splicing

Sometimes this is on purpose, sometimes they have adverse effects

Question 10

What is a spliceosome?

Answer 10

Large ribonucleoprotein complex > splcies primary transcripts to remove introns

Question 11

Does transcription only occur at the promoter regions?

Answer 11

No

Question 12

Where can some RNAs be transcribed from, if not from promoter regions?

Answer 12

Introns

Intergenic regions

Question 13

What is chromatin?

Answer 13

DNA + RNA + protein

Question 14

When is chromatin present?

Answer 14

Only during cell division

Question 15

What must happen to the chromatin for transcription to occur?

Answer 15

Must go from closed to open conformation

Question 16

What proteins have an important role in altering the conformation of chromatin?

Answer 16

Histone proteins

Question 17

What is the most typical chemical modification that happens to DNA?

Answer 17

Methylation

Question 18

What does DNA methylation change?

Answer 18

Conformation of DNA

Question 19

What is nucleosome occupancy?

Answer 19

Density of nucleosome varies along DNA

Question 20

True or false: local location of DNA in nucleus influences its conformation

Answer 20

True

Question 21

What does chromatin remodelling require?

Answer 21

Chemical modification (epigenetic markers) to histones and DNA

Question 22

What effect does DNA methylation have on transcription?

Answer 22

Generally “locks in” transcriptional inactivity

Question 23

How does DNA methylation happen to a new DNA strand?

Answer 23

Large proportion of cytosines in CG adjacent methylated
DNA replication > new DNA strands
New DNA strands initially lack methyl groups
Original pattern of DNA methylation transmitted to daughter cells

Question 24

What are CpG-rich islands associated with?

Answer 24

5’ region of genes

Question 25

What does gene expression or silencing seem to be more related to in terms of methylation?

Answer 25

Methylation status of other CpGs, not CpG islands

Question 26

What is hyper-acetylation of histones associated with in terms of transcription?

Answer 26

Transcriptionally active

Question 27

What is hypo-acetylation of histones associated with in terms of transcription?

Answer 27

Transcriptionally silent

Question 28

What are writer enzymes?

Answer 28

Add on chemical modifications to chromatin

Question 29

What are eraser enzymes?

Answer 29

Remove chemical modifications to chromatin

Question 30

What are reader enzymes?

Answer 30

Read chemical markers on chromatin, and allow other proteins to bind

Question 31

How can transcription be regulated in the gene itself?

Answer 31

Promoters major on-off switches Looping of DNA Direct interactions with other DNA sequences, non-coding RNAs, and trans-acting proteins

Question 32

Do genes only have one promoter?

Answer 32

No, many genes have 1+ promoter

Question 33

What can alternative splicing of different exons lead to?

Answer 33

Different protein products, often tissue specific

Question 34

What are some examples of non-coding RNAs that regulate gene expression?

Answer 34

``` Long non-coding RNAs (lncRNAs) Short interfering RNAs (siRNAs) Micro RNAs (miRNAs) ```

Question 35

What are long non-coding RNAs?

Answer 35

Long enough to fold over and associate with themselves, creating secondary structure

Question 36

What are short interfering RNAs?

Answer 36

Sub-category of long RNAs Complementary to mRNA Degrade mRNA

Question 37

What are micro RNAs?

Answer 37

Not completely complementary to mRNA Binding feeds back to ribosome and represses its activation Reduction of gene expression